GLOSSARY OF AQUATIC ECOLOGICAL TERMS
Environmental Protection Agency
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National Technical Information Service
U. S. DEPARTMENT OF COMMERCE
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GLOSSARY OF AQUATIC ECOLOGICAL TERMS
John E. Matthews
US Department of Commerce
Sptinofield, VA. 22)51
Manpower Development Branch
Air and Water Programs Division
Environmental Protection Agency
Ada, Oklahoma 74820
This Glossary is intended to provide familiarity and under-
standing of technical terminology specific to the discipline of
aquatic ecology and will serve as a convenient reference for all
professionally trained persons concerned with water pollution control.
Definitions have been carefully reviewed to assure accord with
current professional usuage. Appreciation is tendered to biologists
of the following Environmental Protection Agency activities for
this service: Robert S. Kerr Water Research Center, Ada, Oklahoma;
National Field Investigations Center, National Training Center,
Analytical Quality Control Laboratory, Cincinnati, Ohio; National
Water Quality Laboratory, Duluth, Minnesota; National Marine Water
Quality Laboratory, West Kingston, Rhode Island.
Terms specifically identifying or describing organisms have
generally been excluded from this work. For this information the
reader is referred to the selected references presented in the
appendix. Glossaries of terminology related to other disciplines
concerned with water pollution control are also listed in the
Terms underscored in a definition are separately defined
in this Glossary. Where appropriate, closely associated or
related terms are cited parenthetically, (See ), following
the definition. Specific synonyms are noted, in parentheses,
with the listed word.
John E, Matthews
All of a sea, or a very deep lake below the
bathyal zone . The primary energy source for
this region lies far above in the euphotic zone ;
density of life depends on the amount of organic
material that settles from the euphotic zone .
(See Hadal Zone)
Physiological and behavioral adjustments of an
organism in response to a change in environment,
Acclimation of a particular species over
several generations in response to marked
Any toxic effect that is produced within a
short period of time, usually 24-96 hours.
Although the effect most frequently considered
is mortality, the end result of acute toxicity
is not necessarily death. Any harmful biological
effect may be the result. (See Chronic Toxicity ,
Filamentous microorganisms intermediate between
the fungi and bacteria, although more closely
related to the bacteria. These organisms are
widely distributed in soils and are often
conspicuous in lake and river muds. They are
often associated with taste and odor problems
in water supplies.
Change in the structure, form or habits of an
organism to better fit changed or existing
environmental conditions. (See Acclimation)
Refers to life or processes occurring only in
the presence of free oxygen; refers to a
condition characterized by an excess of free
oxygen in the aquatic environment. (See
Simple plants, many microscopic, containing
chlorophyll . Algae form the base of the
food chain in aquatic environments. Some
species may create a nuisance when environmental
conditions are suitable for prolific growth.
Pertaining to those substances, materials or
organisms in a waterway which originate outside
and are brought into the waterway. (See
Pertaining to material that is transported
and deposited by running water.
Synthesis or manufacture of organic compounds
within an organism. (See Metabolism)
Pertaining to fishes that spend most of their
life in salt water but enter freshwater to
spawn ; e.g., salmon, shad, striped bass, etc.
Refers to life or processes occurring in the
absence of free oxygen; refers to conditions
characterized by the absence of free oxygen.
Reduction of the effect of one substance
because of the introduction or presence of
another substance; e.g., one substance may
hinder, or counteract, the toxic influence
of another. (See Synergism )
That portion of a body of water to which
light does not penetrate with sufficient
intensity to have any biological significance.
(See Euphotic Zone )
( Higher Aquatic Plants )
A device placed in the water (for a specified
period of time ) that provides living spaces
for a multiplicity of organisms; e.g., glass
slides, concrete blocks, multiplate samplers,
rock baskets, etc. The primary purpose of
artificial substrates is to allow the investi-
gator to collect organisms in areas where the
physical habitat is limiting or cannot be
adequately sampled using conventional methods.
1. Removal of dissolved or suspended materials
from a water mass by biological, chemical
and physical processes;
2. Conversion or incorporation of absorbed
nutrients into body substances. (See
All organisms occupying a given habitat .
Large, thick, coral mass encircling a lagoon
in tropical oceans; cometimes portions of the
reef become built up with sand, silt, soil and
vegetation to become an island. (See Barrier
Reef , Fringing Reef )
( Periphyton )
Pertaining to those substances, materials,
or organisms originating within a particular
waterway and remaining in that waterway.
Self nourishing; denoting those organisms that
do not require an external source of organic
material but can utilize light energy and
manufacture their own food from inorganic
materials; e.g., green plants, pigmented
flagellates. (See Heterotrophic)
Microscopic, single-celled or noncellular
plants, usually saprophytic or parasitic.
A ridge of deposits separated from the
mainland by an interval of water.
Large, thick, coral mass more or less
surrounding an island or paralleling the
mainland shore in tropical areas; separated
from the land mass by a lagoon. (See Atoll ,
Fringing Reef )
That region of the sea that extends from the
euphotic zone to the bottom of the continental
slope . Density of life in this zone depends
on organic material settling from the euphotic
zone and is generally inversely proportional
to the depth.
The zone of demarcation between land and water
of lakes, seas, etc.; covered by sand, gravel
or larger rock fragments.
The bottom of a waterway; the substratum that
supports the benthos .
Organisms growing on or associated principally
with the bottom of waterways. These include:
(1) sessile animals such as sponges, barnacles,
mussels, oysters, worms, and attached algae;
(2) creeping forms such as snails, worms and
insects; (3) burrowing forms, which include
clams, worms, and some insects; and (4) fish
whose habits are more closely associated with
the benthic region than other zones; e.g.,
A determination of the biological effect of
some substance, factor or condition employing
living organisms or cells as the indicator.
The plants and animals comprising a community .
1. Use of natural predators , parasites or
viruses to reduce or eliminate pest
organisms; e.g., use of gambusia to
feed on mosquito larvae;
2. Control of organisms by interference
with their physiological processes;
e.g., sterilization of male flies.
The ability of certain organisms to remove
from the environment and store in their tissues
substances present at nontoxic levels in the
surrounding water. The concentration of these
substances becomes greater each higher step
in the food chain. (See Enrichment Factor)
The total amount of living material in a
given habitat or area; or, an expression
dealing with the total weight of a given
population of organisms.
1. Continuous surveillance of an effluent
(or dilution thereof) by using living
organisms to test its suitability for
discharge into a receiving water.
2. Use of living organisms to test the
quality of a receiving water downstream
from a waste discharge. (See Bioassay )
A general term used to describe the complex
set of factors involved in the growth of algae
(and other organisms) in a receiving water
due to the addition of nutrients.
All life of a region.
In ecology , those environmental factors which
are the result of living organisms and their
activities; distinct from physical and chemical
factors; e.g., competition , predation, etc.
(See Ecological Factor)
The inherent capability of an animal to multiply
in an unrestricted environment . (See
Midge fly larvae . Many of the species have
hemoglobin in the blood causing a red color
and are often associated with rich organic
deposits. Also, the common name for certain
of the marine segmented worms (class Polychaeta) .
(See Sludgeworms )
A readily visible concentrated growth or
aggregation of minute organisms, usually
algae , in bodies of water.
Those areas where there is a mixture of fresh
and salt water; or, the salt content is
greater than fresh water but less than sea
water; or, the salt content is greater than
in sea water.
Pertaining to animals that feed on other
animals. (See Herbivorous)
The maximum quantity of organisms that any
particular habitat can support over an
The breakdown of organic compounds within an
organism. (See Metabolism)
Pertaining to fish that spend most of their
life in freshwaters; but migrate to the sea
to spawn ; e.g., american eel. (See Anadromous)
Massive drift of bottom organisms under
conditions of stress such as floods or toxicity .
(See Drift Organisms . Incidental Drift ,
A layering of water in a lake because of
density differences owing to the varying or
differential concentrations of dissolved
substances with depth. (See Stratification)
Green photosynthetic pigment present in many
plant and some bacterial cells. There are seven
known types of chlorophyll; their presence
and abundance vary from one group of photosyn-
thetic organisms to another.
Toxicity , marked by a long duration, that
produces an adverse effect on organisms. The
end result of chronic toxicity can be death
although the usual effects are sublethal; e.g.,
inhibits reproduction, reduces growth, etc.
These effects are reflected by changes in the
productivity and population structure of the
community . (See Acute Toxicity)
The placing of organisms into groups (or
categories) according to established scientific
requirements. (See Taxonomy)
An association of organisms found in any
natural, unpolluted environment . These
associations are characterized by the presence
of species that are sensitive to environmental
changes caused by Introduction of pollutants.
In many cases the presence of a wide variety
of species with relatively few individuals
representing any one of them is also a
characteristic. (See Sensitive Organisms ,
A plain between the sea and higher land,
usually at a low elevation.
Those waters surrounding the continent which
exert a measurable influence on uses of the
land and on its ecology . The Great Lakes
and the waters to the edge of the continental
Coastal waters and adjacent lands which exert
a measurable influence on the uses of the sea
and its ecology. The zone extends onshore to
the upper reaches of the tidal zone and adjacent
shore areas. (See Estuary)
Animals that lack an internal temperature
regulating mechanism to offset external
temperature changes. Their body temperature
fluctuates to a large degree with that of
their environment. Examples are fish and
aquatic invertebrates .
A distinguishable localized population within
a species .
An aggregation of organisms within a specified
area; all forms of life inhabiting a common
The depth of a waterway at which there is a
balance between photosynthesis and respiration .
The effort of two or more individuals or
species of a community to utilize some of the
same environmental resources.
COMPETITION No two species can occupy the same niche at
the same time.
Heterotrophic organisms, chiefly animals,
that ingest other organisms or particle
organic matter. Often divided into primary
consumers (Herbivores ) , secondary consumers
( Carnivores which eat primary consumers), etc.
(See Heterotrophic , Trophic Level )
The shallow, gently sloping portion of the
seabottom bordering a continent, down to a
depth of about 200 meters.
The steeply sloping portion of the seabottom
extending seaward from the continental shelf .
A marine member of the phylum Coelenterata
which secretes a hard exoskeleton, chiefly of
Large coral mass associated with coastal areas
in the tropics (See Barrier Reef , Fringing
( Water Quality Criteria )
In bioassays , the range of magnitude of any
factor between the maximum level or concentration
at which no organisms die to the minimum level
or concentration at which all organisms die
under a given set of conditions in a given
period of time.
CULTURAL Acceleration by man of the natural process of
EUTROPHICATION enrichment (aging) of bodies of water.
CULTURE Cultivation of organisms in a medium containing
necessary nutrients .
A fan-shaped deposition of silt, sand, gravel
or other fine materials from a stream. These
occur when the hydraulic gradient lessens
abruptly, as in the discharge of a stream
into a lake, or a river into an ocean.
The number of individuals in relation to the
space in which they occur; refers to the
closeness of individuals to one another
at a given time.
Bottom areas where solids are being actively
deposited because of slackening movement of
the transporting agent. These often occur
in the vicinity of effluent discharges.
(See Sludge Deposits )
Fragments of detached or broken down material.
Toxicity that has an effect on organisms
themselves instead of having an effect by
alteration of their habitat or interference
with their food supply. (See Acute Toxicity ,
Chronic Toxicity , Indirect Toxicity)
1. Refers to an event, process, or specific
change that occurs every day; usually
associated with changes from day to night.
2. Pertaining to those organisms that are
active during day time. (See Nocturnal )
Pertaining to the variety of species within a
given association of organisms. Areas of high
diversity are characterized by a great variety
of species; usually relatively few individuals
represent any one species . Areas with low
diversity are characterized by a few species;
often relatively large numbers of individuals
represent each species.
Species of a community which by their activity,
behavior, or number, have considerable
influence or control upon the conditions of
existence of associated species; species
which "controls" its habitat and food web .
Benthic organisms temporarily suspended in the
water and carried downstream by the current.
(See Incidental Drift , Periodic Drift ,
Catastrophic Drift )
DYSTROPHIC LAKES Shallow lakes with hrown water, high humic
material and organic matter content, low
nutrient availability, poor bottom fauna,
and high oxygen demand; oxygen is continually
depleted and pH is usually low. In lake aging
the "age" between a eutrophic lake and a swamp.
That period of tide between a high water and
the succeeding low water; falling tide.
(See Flood Tide)
Concentration of a substance producing 50%
decrease in shell growth.
Any part or condition of the environment that
influences the life of one or more organisms.
(See Biotic Factor)
The role of an organism in an ecosystem ,
its activities and relationships to the
living and nonliving environment; food
and nutrition relationships are of primary
importance. (See Habitat Niche)
Interrelationships between organisms and their
A community , including all the component
organisms, together with the environment ,
forming an interacting system.
A locally adapted population of a species which
has a distinctive limit of tolerance to envi-
ronmental factors. (Individuals of the same
species may appear different in various
Plants that are rooted at the bottom of a body
of water, but project above the surface; e.g.,
cattails, bulrushes, etc. (See Floating
Aquatic Plants , Submersed Aquatic Plants )
An increase in the quantity of nutrients
available to aquatic organisms for their
growth. (See Eutrophication )
Number of times a substance is concentrated
in the tissue of an organism over the
concentration in its environment. (See
Biological Magnification )
All external influences and conditions affecting
the life and development of an organism or
Restriction imposed on the numerical increase
of a popula tion by environmental factors.
(See Biotic Potential)
The water mass extending from the surface to
the thermocline in a stratified body of water;
the epilimnion is less dense than the lower
waters and is wind-circulated and essentially
homothermous . (See Hypolimnion )
The condition in which a population or community
is maintained with only minor fluctuations in
composition over an extended period of time.
That portion of a coastal stream influenced by
the tide of the body of water into which it
flows; a bay, at the mouth of a river, where
the tide meets the river current; an area
where fresh and marine waters mix. (See
Positive Estuary , Inverse Estuary , Neutral
Estuary , Coastal Zone )
The lighted region of a body of water that
extends vertically from the water surface
to the depth at which photosynthesis fails
to occur because of insufficient light
Prefix meaning wide; e.g., euryhaline refers
to a wide range of salienty tolerance;
eurythermal refers to a wide range of
temperature tolerance. (See Steno- )
Lakes which are rich in nutrients and organic
materials, therefore, highly productive. These
lakes are often shallow and seasonally deficient
of oxygen in the hypolimnion . (See Oligotrophic
EUTROPHI CATION The natural process of the maturing (aging) of
a lake; the process of enrichment with nutrients ,
especially nitrogen and phosphorus, leading to
increased production of organic matter. (See
Cultural Eutrophication , Oligotrophia: Lakes ,
Eutrophic Lakes )
Refers to the capability of an organism to
live under varying conditions; e.g., a
f alcultative anaerobe is an organism that
although usually living in the presence of
free oxygen can live in the absence of free
oxygen. (See Obligate)
A physical phenomenon that may take place in
a body of water during early autumn. The
sequence of events leading to fall overturn
include: (1) cooling of surface waters,
(2) density change in surface waters producing
convection currents from top to bottom,
(3) circulation of the total water volume by
wind action, and (4) vertical temperature
equality. The overturn results in a uniformity
of the physical and chemical properties of the
entire water mass. (See Spring Overturn)
A unit of measurement equal to 6 feet (1.83
Animal life .
A narrow arm of the sea; also the opening of
a river into the sea. (See Estuary)
A narrow arm of the sea between highlands .
(See Firth . Estuary)
Rooted plants that wholly or In part float
on the surface of the water; e.g., water lilies,
water hyacinth and duckweek. (See Emersed
Aquatic Plants , Submersed Aquatic Plants)
That period of tide between low water and the
succeeding high water; a rising tide. (See
Of or pertaining to rivers; growing or living
in streams; produced by river action, as a
Dependence of a series of organisms, one upon
the other, for food. The chain begins with
plants and ends with the largest carnivores;
e.g. , phytoplankton ■»■ zooplankton ■* forage
fish -*■ game fish.
All the interconnecting food chains In a
Fish, usually smaller prolific species, that
are important as food for predatory species.
Actively moving about in water or capable of
moving about in water. (See Sessile)
FRINGING REEF Large coral mass at the edge of any land mass
In tropical seas; It begins at the water's
edge and may extend out to a quarter mile.
(See Barrier Reef, Atoll)
Those species of fish considered to possess
sporting qualities on fishing tackle; e.g.,
salmon, trout, black bass, striped bass, etc.
Game fish are usually considered to be more
sensitive to environmental changes than
rough fish .
( Competition-Exclusion Principle)
A specific type of place that is occupied by
an organism , a population , or a community .
( Ecotype )
The specific part or smallest unit of a habitat
occupied by an organism. (See Ecological Niche )
Pertaining to that part of the ocean at depths
exceeding 6000 meters, including both water
and floor or bottom. (See Abyssal Zone)
A chemical substance used for killing plants,
An organism that feeds on plant material,
Consisting of dissimilar elements or constituents,
(See Homogeneous )
Pertaining to organisms that are dependent
on organic material for food. (See Autotrophic )
Those plants composed of complex and differentiated
tissues whose seeds germinate in the water phase or
substrate of a body of water and which must spend
part of their life cycle in water. This grouping
includes plants which grow completely submersed
as well as a variety of emersed and floating leaf
types. (See Macrophyte )
( Autotrophic )
( Heterotrophic )
Of uniform composition throughout.
Having the same temperature throughout.
The region of a body of water that extends
from the thermocline to the bottom and is
essentially removed from major surface
influences. (See Epilimnion )
The use of a taxonomic key or the equivalent
to determine the scientific name of an organism.
The casual, random drift of organisms.
(See Drift Organisms , Catastrophic Drift ,
That concentration of an environmental identity
beyond which an organism could no longer
survive for an indefinite period of time.
A species , whose presence or absence may be
characteristic of environmental conditions in
a particular area or habitat ; however, species
composition and relative abundance of individual
components of the population or community are
usually considered to be a more realiable
index of water quality.
Refers to an organism that is native, not
introduced in an area.
Toxicity that affects organisms by interfering
with their food supply or modifying their
habitat instead of directly acting on the
organisms themselves. (See Direct Toxicity )
A short, narrow waterway connecting a bay,
lagoon , or similar body of water with a large
parent body of water; an arm of the sea, or
other body of water, that is long compared to
its width, and that may extend a considerable
A stage in the life cycle of an insect or other
arthropod between two successive molts .
Mutual or reciprocal action or influence between
organisms, between organisms and environment ,
or between environmental factors.
Refers to relations or conditions between
species . (See Intraspecific )
( Sensitive Organisms )
Refers to relations or conditions between
individuals within a species . (See
Type of est ary in which evaporation exceeds
the supply of freshwater; evaporation >
freshwater inflow + precipitation. (See
Positive Estuary , Neutral Estuary )
Animals without an internal skeletal structure;
e.g., insects, mollusks, crayfish. (See
1. A shallow sound, pond, or channel near
or communicating with a larger body of
2. A settling pond for treatment of wastewater.
The immature form of an animal which is unlike
its parents. Larva are usually self-feeding
but must pass through some sort of metamorphosis
before assuming the characteristics of the
adult; in insects, the wormlike stage between
the egg and the pupa .
LAW OF THE MINIMUM,
"The growth and reproduction of an organism
is dependent on the nutrient substance, such
as oxygen, carbon dioxide, calcium, etc., that
is available in minimum quantity." (See
Limiting Factor )
LAW OF TOLERANCE,
SHELFORD ' S
"When one environmental factor or condition is
near the limits of toleration, either minimum
or maximum, that one factor or condition will
be the controlling one and will determine
whether or not a species will be able to
maintain itself." (See Limiting Factor)
Pertaining to standing (nonflowing) waters
such as lakes, ponds, and swamps. (See Lotic)
The various phases, changes, or stages through
which an individual passes from the fertilized
egg to death of the mature organism. (See
A factor whose absence, or excessive concentration,
exerts some restraining influence upon a
population through incompatibility with species
requirements or tolerance . (See Law of the
Minimum , Law of Tolerance)
The open -water region of a lake, especially in
areas too deep to support rooted aquatic plants.
This region supports plankton and fish as the
principal plants and animals . (See Littoral
The ecology of fresh waters .
The shallow area that extends from shore to
the lakeward limit of rooted aquatic plants;
the shoreward region of a body of water; in
marine ecology , the tidal zone . (See Limnetic
Pertaining to flowing waters such as streams
and rivers. (See Lentic)
MACROORGANISMS Those organisms visible to the unaided eye
(Macroinvertebrates) ^ wh±ch ^ retained on a u. S . standard
sieve no. 30 (openings of 0.589 mm.). (See
Any plant that can be seen with the naked,
unaided eye; e.g., aquatic mosses, ferns,
liverworts, rooted plants, etc.
An earthy, unconsolidated deposit formed in
freshwater lakes, chiefly of calcium carbonate
mixed with clay or other impurities in
Periodically wet or continually flooded area
with the surface not deeply submerged. Covered
dominantly with emersed aquatic plants ; e.g.,
sedges, cattails, rushes.
The concentration of tested substance in
water at which just 50% of the test organisms
survive for a specified period of exposure.
(See Tolerance Limit)
Lakes in which dissolved substances create
a gradient of density differences with depth;
this prevents complete mixing or circulation
of water masses. (See Chemical Stratification)
A condition of permanent stratification of
water masses in lakes.
The sum of all chemical processes occurring
within an organism; includes both synthesis
(anabolism) and breakdown ( catabolism ) of
Abrupt transformation of an animal from one
distinctive life history stage to another
in its postembryonic development; e.g.,
larva of an insect to a pupa . (See Life Cycle )
MICROORGANISMS Those minute organisms invisible or only barely
(Microinvertebrates) . .., , ,, .
visible to the unaided eye. Microorganisms
pass through a U. S. standard series no. 30
sieve but are retained on a no. 100 sieve
(openings of 0.149 mm). (See Macroorganisms)
To cast or shed periodically the outer body
covering which permits an increase in size.
This is especially characteristic of inverte-
brates. (See Ins tar)
( Free-Swimming )
Very minute p lankton not retained in a plankton
net equipped with no. 25 silk bolting cloth
(mesh, 0.03 to 0.04 mm.).
A species that is part of an area's original
Processes occurring in nature which result in
survival of the fittest and elimination of
individuals less well adapted to their
Free-swimming microscopic larval stage
characteristic of many crustaceans, barnacles,
Exceptionally low tides which occur twice each
month when the earth, sun and moon are at
right angles to each other; these usually
occur during the moon's first and third
quarters. (See Spring Tides )
Macroscopic organisms swimming actively in
water; e.g., fish. (See Plankton )
Relatively shallow water zone which extends
from the high-tide mark to the edge of the
Plankton retained in a plankton net equipped
with no. 25 silk bolting cloth (mesh, 0.03
to 0.04 mm. ) .
Organisms associated with, or dependent
upon, the surface film (air-water interface)
of bodies of water.
Type of estuary in which neither the freshwater
inflow nor the evaporation predominates;
freshwater inflow + precipitation - evaporation.
(See Positive Estuary , Inverse Estuary)
(See Ecological Niche. Habitat Niche)
Pertaining to those organisms that are active
at night. (See Diurnal)
Those organisms capable of interfering with
the use or treatment of water.
Elements, or compounds, essential as raw
materials for organism growth and development;
e.g., carbon, oxygen, nitrogen, phosphorus,
An immature developmental form characteristic
of the pre-adult stage in insects that do not
have a pupal stage; e.g., mayflies and
stoneflies. (See Larva)
Limited to one mode of life or action. (See
The region of open ocean beyond the continental
Deep lakes which have a low supply of nutrients,
thus they support very little organic production .
Dissolved oxygen is present at or near saturation
throughout the lake during all seasons of the
year. (See Eutrophic Lakes)
Feeding on both plant and animal tissue. (See
The most suitable degree of an environmental
factor for the full development of the organism
concerned. (See Tolerance Range)
Any living individual.
The adjustment in the osmotic concentration of
solutes in body fluids in organisms to
environmental conditions; e.g., when salmon
migrate from salt to freshwater.
The period of mixing, by top to bottom circulation,
of previously stratified water masses . This
phenomenon may occur in spring and/or fall; the
result is a uniformity of physical and chemical
properties of the water at all depths. (See
Thermal Stratification , Chemical Stratification ,
Spring Overturn , Fall Overturn)
A temporary phenomenon that occurs in an
organism when available oxygen is inadequate
to supply the respiratory demand. During
such a period the metabolic processes result
in the accumulation of breakdown products that
are not oxidized until sufficient oxygen
The difference between observed oxygen
concentration and the amount that would
theoretically be present at 100% saturation
for existing conditions of temperature and
An organism that lives on or in a host organism
during all or part of its existence. Nourishment
is obtained at the expense of the host.
An organism or virus that causes a disease.
The open sea, away from the shore. Comparable
with the limnetic zone of lakes .
Drift of bottom organisms at regular or
predictable intervals such as diurnal ,
seasonal, etc. (See Drift Organisms .
Catastrophic Drift . Incidental Drift)
Attached microscopic organisms growing on
the bottom, or other submersed substrates ,
in a waterway.
Any chemical preparation used to kill pests .
Includes insecticides, herbicides, fungicides,
The metabolic process by which simple sugars
are manufactured from carbon dioxide and
water by plant cells using light as an
energy source. (See Chlorophyll)
( Euphotic Zone)
The plants of the plankton . Unattached
microscopic plants subject to movement by
wave or current action. (See Zooplankton)
Suspended microorganisms that have relatively
low powers of locomotion, or that drift in
the water subject to the action of waves and
currents. (See Benthos, Periphyton , Nekton)
(Higher Aquatic Plants)
Areas of a stream, where the velocity of
current is reduced. The reduced velocity
provides a favorable habitat for plankton .
Silts and other loose materials that settle
to the bottom of pools are favorable for
burrowing forms of benthos . (See Riffle)
A group of interacting individuals of the
same species , area , or community .
Coastal indentures in which there is a
measurable dilution of sea water by land
drainage; freshwater inflow + precipitation >
evaporation. (See Inverse Estuary, Neutral
Stream reach at lower elevations characterized
by reduced flow, higher temperature, and
lower dissolved oxygen levels . (See Rithron
An animal that kills and consumes other
animals. (See Prey)
Those organisms that are of outstanding
abundance in a particular community for a
given period of time. (See Dominant)
An animal that is killed and consumed by
another animal. (See Predator)
The total quantity of protoplasm produced by
autotrophic organisms per unit of time in a
specified habitat .
Organisms that synthesize organic material
from inorganic substances; e.g., plants.
(See Consumers , Reducers)
The process of producing organic material; the
1. Rate of protoplasm formation or energy
utilization by one or more organisms ;
total quantity of organic material
produced within a given period in a
specified habitat .
2. Capacity or ability of an environmental
unit to produce organic material. (See
Primary Productivity , Secondary Productivity)
The deep, bottom-water area beyond the depth
of effective light penetration. All of the
lake floor beneath the hypolimnion .
Pertaining to organisms that have a high
reproduction rate and normally produce large
numbers of young.
The living material in cells of plants and
An intermediate, usually quiescent , form
following the larval stage in insects, and
maintained until metamorphosis to the
adult stage. (See Larva)
QUALITY A term to describe the composite chemical,
physical, and biological characteristics of
a water with respect to its suitability
for a particular use.
QUIESCENT Refers to the temporary cessation of development.
movement or other activity. (See Puoa)
Areas of a stream where velocity of current
is great enough to keep the bottom clear of
all loose materials, thus providing a firm
substrate . The surface of the water is
disrupted by turbulent currents. This area
is occupied largely by specialized benthic
or periphytic organisms that can firmly attach
or cling to a firm substrate . (See Pools ,
A visible red-to-orange coloration of an
area of the sea caused by the presence of a
bloom of certain plankton . These blooms are
often the cause of major fish kills.
A type of fish spawning area associated with
flowing water and clean gravel. Fishes that
utilize this type of spawning area include
trout, salmon, some minnows, etc.
Those organisms, usually bacteria or fungi,
that break down complex organic material into
simpler compounds. (See Producers , Consumers)
A ridge of rocks, sand, soil or coral projecting
from the bottom to or near the surface of the
wat er .
The complex series of chemical and physical
reactions in all living organisms by which
the energy and nutrients in foods is made
available for use. Oxygen is used and carbon
dioxide released during this process. (See
A shallow rapids in an open stream where the
water surface is broken into waves by wholly
or partly submerged obstructions. Riffles
usually support a wider variety of bottom
organisms than other stream sections. (See
Stream reach at higher elevations characterized
by rapid flow, low temperature, and high
dissolved oxygen levels. (See Potamon Zone )
Those species of fish considered to be of
poor fighting quality when taken on tackle;
e.g., carp, gar, suckers, etc. These fish
are considered undesirable in most situations,
Most species in the group are more tolerant
of widely changing environmental conditions
than game fish .
Low area adjacent to the sea that is covered
with salt tolerant vegetation and regularly
flooded by high tide; similar inland
areas near saline springs or lakes , though
not regularly flooded.
Living on dead or decaying organic matter.
The sum of all metabolic processes which are
the direct opposite of primary production ;
can be measured either by the dynamics of
metabolism or analysis of community structure.
European system of classifying organisms
according to their response to organic
pollution in slow moving streams.
1. Alpha-Mesosaprobic Zone - Area of active
decomposition, partly aerobic , partly
anaerobic , in a stream heavily polluted
with organic wastes.
2. Beta-Mesosaprobic Zone - That reach of a
stream that is moderately polluted with
3. Oligosaprobic Zone - That reach of a
stream that is slightly polluted with
organic wastes and contains the mineralized
products of self-purification from organic
pollution, but with none of the organic
4. Polysaproblc Zone - That area of a
grossly polluted stream which contains
the complex organic wastes that are
decomposing primarily by anaerobic
An organism that consumes decomposing organic
Total quantity of animal (and other
heterotrophic ) protoplasm produced per unit
of time in a specified habitat . (See Primary
Productivity , Productivity )
Periodic oscillations in the water level of
a lake or other landlocked body of water due
to unequal atmospheric pressure, wind, or other
cause, which sets the surface in motion. These
oscillations take place when a temporary local
depression or elevation of the water level occurs.
Organisms that exhibit a rapid response to
environmental changes and are killed, driven
out of the area, or as a group are substantially
reduced in numbers when their environment is
fouled. (See Tolerant Association)
Pertaining to those organisms that are
attached to a substrate and not free to
move about; e.g., periphyton . (See Free-
All material, both organic and inorganic,
suspended in a waterway. Bioseston is the
living material; abioseston is the non-living
Accumulations of settled, usually rapidly
decomposing, organic material in the aquatic
system. A deposit of solids of wastewater
Substances of viscous organic nature, usually
formed from microbiological growth.
Aquatic segmented worms (class - Oligochaeta)
that exhibit marked population increases in
waters polluted with decomposable organic
wastes. (See Bloodworms)
1. In aquatic animals, to produce or deposit
eggs or sperm.
2. To produce eggs or young.
3. Eggs of fishes and higher aquatic
An organism or organisms forming a natural
population, or groups of populations , that
transmit specific characteristics from
parent to offspring. Each species is
reproductively isolated from other populations
with which they might breed. Hybrids, the
results of interbreeding, usually exhibit a
loss of fertility.
A physical phenomenon that may take place
in a body of water during the early spring.
The sequence of events leading to spring
overturn include: (1) melting of ice cover,
(2) warming of surface waters, (3) density
changes in surface waters producing convection
currents from top to bottom, (A) circulation
of the total water volume by wind action, and
(5) vertical temperature equality. The
overturn results in a uniformity of the
physical and chemical properties of the entire
water mass. (See Fall Overturn, Overturn)
Exceptionally high tide which occurs twice
per lunar month when there is a new or full
moon, and the earth, sun, and moon are in a
straight line. (See Neap Tides )
( Water Quality Standard )
The quantity of living organisms present in
an environment at a selected point in time.
Prefix denoting a narrow range of tolerance
of an organism to a specific environmental
factor; e.g., stenothermal refers to temperature;
stenohaline refers to salienity; etc. (See Eury-)
An influence that causes a response in an
organism. (See Taxis )
Arrangement of water masses into separate,
distinct, horizontal layers as a result of
differences in density; may be caused by
differences in temperature, dissolved or
suspended solids. (See Thermal Stratification ,
The conditions resulting from any environmental
change that disturbs the normal functioning of
an animal to such an extent that its chances
for survival are reduced.
The part of the shore from the lowest water
level to the lower boundary of plant growth;
transition zone from the littoral to
Higher aquatic plants that grow, or are
adapted to grow, beneath the surface of the
water; e.g., pondweed, coontail, etc.
The bottom material of a waterway; the base
or substance upon which an organism is growing;
a substance undergoing oxidation.
Complete or partial kill of a fish population
in ponds or lakes during the warm months;
variously produced by excessively warm water,
by a depletion of dissolved oxygen, and by
the release of toxic substances from a decaying
algal bloom, or by a combination of these
factors. (See Winter Kill)
The portion of the seashore adjacent to the
tidal or spray zone.
( Floating Aquatic Plants)
Two organisms of different species living
in close association , one or both of which
may benefit and neither is harmed. Such a
phenomenon is found among organisms in biological
The joint action of two or more substances is
greater than the sum of the action of each
of the individual substances; e.g., action of
certain combinations of toxicants . The
improvement in performance achieved because
two agents are working together. (See
The production of a substance by the union
of elements or simpler chemical compounds.
( Taxonomy )
Directed movement by an organism in response to
a stimulus ; e.g., photo taxis is directed movement
in response to a light stimulus; thermo taxis is
directed movement in response to heat or cold
as a stimulus; etc.
A "kind" of organism . - Any taxonomic unit or
category of organisms; e.g., species, genus,
family, order, etc.
Organism classification with reference to their
precise relationship in the plant or animal
kingdom; includes the bases, principles,
procedures and rules of classification.
Growing, living, or peculair to the land, as
opposed to the aquatic environment.
The area which an animal defends against
The layering of water masses owing to different
densities in response to temperature. The
condition of a body of water in which the
successive horizontal layers have different
temperatures , each layer more or less sharply
differentiated from the adjacent ones, the
warmest (or the coldest) at the top. (See
The transition zone between the warm epilimnion
and cold hypolimnion of stratified bodies of
water; temperature change equals or exceeds
1°C for each meter of depth. (See Thermal
The maximum or minimum duration or intensity
of a stimulus that is required to produce a
response in an organism.
The sea bottom, usually wide, flat, muddy and
nonproductive, which is exposed at low tide. A
marshy or muddy area that is covered and
uncovered by the rise and fall of the tide.
A low, flat marshland that is traversed by
interlacing channels and tidal sloughs;
periodically inundated by high tides; vegetation
consists of rushes, grasses, and other salt
The area of a shore between the limits of
water level fluctuation; the area between
the levels of high and low tides .
The alternate rising and falling of water
levels, twice in each lunar day, due to
gravitational attraction of the moon and sun
in conjunction with the earth's rotational
TL* (TL 50 )
(Median Tolerance Limit)
Relative capability of an organism to endure
or adapt to an unfavorable environmental
(TL 10...100 )
The concentration of a substance which some
specified portion of an experimental population
can endure for a specified period of time with
reference to a specified type of response; e.g.,
TL 100 means tna t all test organisms endured
the stress for the specified time; TLiq means
only 10% of the test organisms could tolerate
the imposed stress for the specified time.
(See Median Tolerance Limit)
The range of one or more environmental
conditions within which an organism can
function; range between the highest and
lowest value of a particular environmental
factor in which an organism can live.
An association of organisms capable of
withstanding adverse conditions within the
habitat . This association is often characterized
by a reduction in the number of species (from
a clean water association ) and, in the case of
organic pollution, an increase in individuals
representing certain species.
A substance that through its chemical or
physical action kills, injures, or impairs
an organism; any environmental factor which,
when altered, produces a harmful biological
effect. (See Pesticide)
Quality, state or degree of the harmful effect
resulting from alteration of an environmental
The dead suspended particulate matter in
aquatic habitats; the nonliving portion of
One of the parts in a nutritive series in an
ecosystem in which a group of organisms in a
certain stage in the food chain secures food
in the same general manner. The first or
lowest trophic level consists of producers
(green plants) ; the second level of herbivores ;
the third level of secondary carnivores .
Most bacteria and fungi are organisms in the
reducer (decomposer) trophic level.
The area of a body of water where organic
production from mineral substances takes
place on the basis of light energy and
The deep area of a body of water where organic
breakdown predominates because of light
Organisms that can tolerate a wide range of
environmental conditions or variation; organisms
that are so active or numerous as to seem to
be present or existent in all types of
environments. (See Tolerant Association.
Sensitive Organisms )
Refers to an organism that consists of only
one cell; e.g., blue green algae, protozoa,
bacteria. These organisms may, however,
be filamentous or colonial in form.
VERTEBRATES Animals that have an internal skeletal
system. (See Invertebrate)
Alteration of the aquatic environment in
such a way as to interfere with a designated
"A scientific requirement on which a decision
or judgement may be based concerning the
suitability of water quality to support a
designated use." (See Water Quality Standard )
"A plan that is established by governmental
authority as a program for water pollution
prevention and abatement." (See Water Quality
The death of fishes in a body of water during
a prolonged period of ice and snow cover;
caused by oxygen exhaustion due to respiration
and lack of photosynthesis. (See Summer Kill )
ZONE An area characterized by similar flora
or fauna; a belt or area to which certain
species are limited.
ZOOPLANKTON The animals of the plankton . Unattached
microscopic animals having minimal capability
SELECTED REFERENCES ^ ^
Anon. Glossary - Water and Wastewater Control Engineering.
Prepared by Joint Editorial Board Representing APHA, ASCE,
AWWA, WPCS. 1969.
Anon. Report of The Committee on Water Quality Criteria. USDI,
Anon. Resource Conservation Glossary. Soil Conservation
Society of America. Ankeny, Iowa. 1970.
Edmonson, W. T. (Editor). Ward and Whipple's Freshwater Biology.
Second Edition. John Wiley & Sons, Inc. New York. 1959.
Geckler, J. R. , K. M. Mackenthun and W. M. Ingram. Glossary of
Commonly Used Biological and Related Terms in Water and Waste
Water Control. USDHEW, PHS No. 999-WP-2. 1963.
Hanson, H. C. Dictionary of Ecology. Philosophical Library.
New York. 1957.
Ingram, W. M. , K. M. Mackenthun and A. F. Bartsch. Biological Field
Investigative Data for Water Pollution Surveys. USDI, FWPCA,
WP-13. Pages 17-46. 1966.
Kenneth, J. H. (Editor). A Dictionary of Biological Terms. Eighth
Edition. D. Van Nostrand Company, Inc. New York. 1963.
Ludzack, F. J. Glossary of Wastewater and Surface Water Technology.
Reference Outline Series. USDI, FWPCA, National Training Center,
Needham, J. G. and P. R. Needham. A Guide to the Study of Freshwater
Biology. Fifth Edition. Holden-Day, Inc. San Francisco. 1962.
Odum, E. P. Fundamentals of Ecology. W. B. Saunders Company.
Pennack, R. W. Collegiate Dictionary of Zoology. The Ronald Press
Co. New York. 1964.
Pennack, R. W. Fresh-Water Invertebrates of the United States.
The Ronald Press Co. New York. 1953.
Rechard, P. A. and R. McQuisten. Glossary of Selected Hydrologlc
Terms. Water Resources Research Institute, University of
Wyoming, Laramie. Water Resources Series No. 1. 1966 (Revised
Reid, G. K. Ecology of Inland Waters and Estuaries. Reinhold
Publishing Corporation. New York. 1961.
Ruttner, F. Fundamentals of Limnology. University of Toronto Press.
Third Edition. Toronto, Ontario. 1963.
Stewart, K. M. and G. A. Rohlich. Eutrophication - A Review. A
Report to the State Water Quality Control Board, California.
Publication No. 34. Sacramento. 1967.
Storer, T. I. and R. L. Usinger. General Zoology. McGraw-Hill Book
Co., Inc. New York. 1957.
Sverdrup, H. U. , M. W. Johnson and R. H. Fleming. The Oceans,
Their Physics, Chemistry, and General Biology. Prentice Hall,
Inc. New York. 1942.
Welch, P. S. Limnology. Second Edition. McGraw-Hill Book Co.
New York. 1952.
* US.eOVH»«(0«TI>l<llt™GOfnCfcl972- 759-303/2118